The present invention relates to a xe2x80x9cHolterxe2x80x9d-type apparatus for recording physiological signals indicative of a patient""s cardiac activity, which signals are collected (i.e., sensed) by external electrodes applied to the patient, and more particularly to a portable Holter-type apparatus intended to provide uninterrupted, long-term, ambulatory recording of cardiac activity signals.
Holter recording devices are known which traditionally use an analog or digital recording technique. These devices typically have either a magnetic cassette tape or a static digital memory, and batteries, which are disposed in a case. Cables are used to connect the case to the electrodes which are coupled to the patient for collecting the signals to be recorded.
The case is then worn by the patient, either over the shoulder as a shoulder-belt-type harness or attached to a belt around the waist or other body part of the patient.
A major disadvantage of these known Holter devices arises from the discomfort to and inconvenience suffered by the patient because of the interference caused by the cables, for example, when bathing, taking a shower, changing clothes. In such cases, the cables can become ensnarled in the patient""s clothing or movements, and the apparatus can become dislodged and quite possibly may fall to the ground. In addition, as the patient must remain in close physical proximity to the apparatus when used during sleeping, he or she runs the risk of turning over and crushing the apparatus or accidentally ripping the cables out of their sockets, for example, when getting up. Further, certain types of clothing, and in particular women""s clothing, do not allow for easy passage of the cables between the thorax and the electrodes on the recorder case, particularly when the recorder is worn in an over-the-shoulder position.
It is, therefore, an object of the present invention to remedy the disadvantages described above by proposing a new Holter apparatus structure, which is particularly compact and which additionally minimizes a patient""s discomfort.
Broadly, the present invention is directed to a Holter system having a xe2x80x9csolexe2x80x9d or xe2x80x9cbasexe2x80x9d unit, which incorporates the electrodes and their respective electric connections, and a recording case affixed directly to the base unit. Thus, the recording case, instead of being fastened to a belt or carried over-the-shoulder in a shoulder belt and connected by cables to the patient, will be supported directly by the base unit, eliminating the need for cables and the problems caused by the cables. The interconnected case and base unit thus provide a xe2x80x9cwirelessxe2x80x9d Holter recording device which is supported by electrodes on the patient.
In a preferred embodiment, the invention is directed towards an apparatus, including a base unit, that is formed of a flexible sheet carrying electrodes and conductive connection elements. The base unit has a central area for receiving a recording case, which attaches to the base unit. The base unit central area also is equipped with contact areas which are the proximal terminations of the respective conductive connection elements. In this embodiment, the recording case has a means for attaching to the central area of the base unit, and electrode contacts which are configured to make the appropriate electrical contacts with the proximal termination areas of base unit conductive connection elements.
In one embodiment, the central area of the base unit forms a thoracic belt or strap, which serves as the support for the recording case. In other words, the recording case means for attaching structure functions to attach the recording case to the thoracic belt of the base. Preferably, the base unit also carries a battery to supply power to the recording to the recording case.
The base unit is preferably made of a sheet of flexible printed circuit material on which is etched or engraved a conductive pattern forming the aforementioned electrodes, contact areas and conductive connection elements connecting the electrodes to their respective contact areas.
The recording case is preferably a two-piece structure having a base and a cover that, when closed, secures the recorder base firmly to the base unit in electrical contact. More preferably, the recorder case and cover have a hinge, even more particularly an articulated hinge, along a common side. Advantageously, the recording case also comprises a peripheral seal surrounding at least the aforementioned electrode contact areas and, if necessary, the battery contact points of the base unit, so as to provide fluid resistance for the electrical connections.
The recording case and the base also preferably comprise cooperating structures for respectively centering and supporting the assembly. For example, protruding studs and cooperating holes or detents respectively mounted on the base unit and recording case, or vice versa, or in different combinations, may be used to position the recording case securely to the base unit in the proper orientation and without relative movement there-between.